1. Field of the Invention
This invention relates generally to the field of portable parts washing apparatus, and particularly to a portable parts washing apparatus having a centrifugal filter to separate foreign waste elements from a cleaning solvent.
2. Background Art
Parts washers are widely used in industrial applications, and in particular, automotive service shops. The most familiar part washer can be found in almost any service station in the country. It is comprised of a sink with a spigot and a drain that sits upon a standard 55 gallon drum. The drum is partially filled with a parts washing solvent. The solvent is pumped from the drum, through the spigot, where it flows over the dirty part, into the sink's drain, from which it falls back into the drum. In this manner, the solvent continuously flows over the dirty part while the operator washes the part in the sink.
There has long been an unmet need for a portable parts washer that can be easily moved to a field location. An example of such an unmet need is military deployment. Military equipment in use in the field requires maintenance that cannot be done in a regular service shop either because of logistics or simply convenience. A portable parts washer would also be useful for applications outside of the military. For example, repairing and maintaining heavy machinery on site of a construction project or at a logging camp. It has been impractical to move parts washers to the field because of their size, weight, and configuration. As a substitute for this very useful device, a parts washer in the field consists of a bucket filled with solvent in which a part is dipped and washed by hand. The bucket is emptied when the solvent becomes saturated with dirt. This practice is inefficient, wasteful, and environmentally hazardous.
Despite the multitude of advantages over the bucket method that the basic configuration of the parts washer (sink, barrel and solvent moving means) has, it is believed that few, if any, conventional parts washers are used during a military deployment. This is largely because conventional parts washers are impractical to move and take up much more cargo space than justifies their use. The sink portion of the conventional parts washers are made of steel for fire safety reason and are therefore very heavy. In addition, a typical 55 gallon drum half-filled with solvent could easily weigh several hundred pounds. Since the pump of these conventional parts washers is most often suspended from below the sink, damage during transport is very likely. Exposed this way, it is almost certain that the bracket, the pump, the hoses, or any combination of the three would be damaged. The parts washer would also take up a great deal of space, space that is at a premium on a military deployment.
Of the many patents discussed below that are concerned directly with parts washers, only U.S. Pat. No. 4,462,415 (Otzen) even teaches a solvent tank designed to be taken to a reclamation facility to be exchanged for fresh solvent. This patent describes a low cost parts washer intended for use by the occasional user and adapted for self-service fluid changes. The unit has a modular solvent tank of modest capacity that can be removed from the parts washer, capped in several places, and returned to a distributor for exchange with a solvent tank containing fresh solvent. There is no filtering means inside the solvent tank.
In addition to being impractical to move, the problem with conventional parts washers is that the foreign material washed from the dirty part flows into the drum along with the solvent. In many applications, the foreign material will be comprised of metal shavings, dirt, sand, grit, and oil particulates. Since much of this debris will remain suspended in the solvent while the pump is running, the pump is continuously subjected to substances that will damage its internal seals. Much of the background art in this area has addressed this particular problem by placing a filter upstream of the pump to strain the foreign debris from the solvent before it reaches the pump. For instance, in U.S. Pat. No. 4,056,114 (Boutillete), the pump is surrounded by a filter element. U.S. Pat. No. 3,890,988 (Lee) teaches a pump mounted at the top of a truncated cone that rests at the bottom of a solvent tank. The cone is made from a screen that is intended to filter the solvent before it reaches the inlet of the pump. U.S. Pat. No. 5,464,533 (Koslow) teaches a two stage active filter that is located inside an extended pump housing. Instead of having the filter continuously in line with the pump, U.S. Pat. No. 5,368,653 (Russell) teaches a filter that can be periodically used at the discretion of the user.
Trapping the gunk and the solvent together until the solvent drains from the filter, however, insures that the gunk will retain a substantial amount of the solvent. This wet waste material will eventually condense into a thick, gummy, oily substance, commonly referred to in the art as "gunk."
In U.S. Pat. No. 3,378,019 (Riolo et al.) the patent teaches a paper filter located below the drain. The solvent flows through the filter with only the assistance of gravity. Similarly, in U.S. Pat. No. 3,960,728 (Otzen) a filter bag is described that hangs from the drain. U.S. Pat. No. 5,522,814 (Olson) teaches a gravity filter comprising a compartment filled with waste cotton located below the drain. U.S. Pat. No. 2,675,012 (Scales) notes that these types of gravity filters are quickly obstructed by the gunk and will not filter the solvent. Accordingly, Scales teaches a complex set of superposed sludge settling trays of successively decreasing diameters. In U.S. Pat. No. 4,226,548 (Reith) the sludge trap is located under a screen that covers the interior bottom of the sink. The solvent flows over a ridge to a drain while the sediment settles on the other side of the ridge.
Other techniques proposed include skimming the waste materials that float on top of an aqueous cleaning solution as is taught in U.S. Pat. No. 5,303,725 (Hilgren), or simply distributing the solvent as it drains so it does not upset the sediment that has collected at the bottom of the drum as is described in U.S. Pat. No. 4,505,284 (Kyatt). U.S. Pat. No. 2,085,075 (Delano) teaches a portable crankcase flusher and cleaner that introduces, extracts, and filters cleaning fluid from the crankcase of an automobile using a complicated reversible one-way valve. Solvent is introduced to the crankcase, removed and cycled trough a centrifuge, and returned to the crankcase several times. The second major effect of the foreign matter flowing freely into the drum along with the solvent is that, as the foreign material settles to the bottom of the drum it will accumulate and condense into gunk. This gunk layer will eventually foul, and probably damage, the pump. In any case, the solvent in the drum will eventually be so full of gunk and suspended matter that it will have to be replaced and the old solvent disposed of. In the age before hazardous waste laws, this problem was addressed in the art by using plastic drum liners that would capture the solvent, the foreign materials, and the gunk so that they could all be disposed of together--probably ending up in a landfill (assuming the liner made it that far without being punctured). This disposable liner concept is taught in U.S. Pat. Nos. 3,890,988 (Lee). 3,552,814 (Olson); 4,056,114 (Boutilette).
Contrary to a suggestion in the Lee patent, it is no longer possible to remove the gunk and solvent together in a plastic liner to be disposed of in a landfill or, for the matter, in the dirt behind the service station. The solvents used in parts washers are now classified as hazardous waste materials and are heavily regulated by both state and federal law. There are severe civil and criminal penalties for the improper disposal of the waste materials associated with these parts washers. Similarly, it is no longer practical to clean the gunk from the parts washers because the gunk still has to be disposed of as hazardous waste.
Because of the hazardous waste laws, a huge industry has developed to service parts washers. The 1995 annual report from the largest of these service providers reports reclaiming more than 210 million gallons of contaminated fluids and discloses revenues in this area are in excess of $240 in dollars per year. Servicing the parts washers usually means removing the sink from the drum, capping the used drum off, and transporting the used solvent and gunk contained in the drum to a reprocessing plant. Evidencing the major concern that the industry has over hazardous waste liability, this service provider also advertises that it indemnifies the customer against liability hazardous waste spills that may occur while the solvent is being transported.
In the portable applications such as is described in the present application, the significance of the environmental concerns often comes second to the need for the solvent to remain mostly waste free for relatively long periods of time under heavy use. In the example of a military deployment, the fewer parts washers that need to be deployed, the less the supply lines are burdened. It is axiomatic that the fewer parts washers available in the field, the harder they will be used.
Perhaps most importantly, many of the designs discussed above rely on the solvent tank remaining stationary so that the waste materials settle to the bottom of the tank where they are out of the way. The motion inherent in moving the solvent tank from one location to another would freely mix the waste materials back into the solvent, making many of the methods involved in the previous patents ineffective, and the moving of the conventional parts washer to another location almost useless.